Binaural telephone system



1927. April 12 H. FLETCHER ET AL BINAURAL TELEPHONE SYSTEM Filed June 1925 Mraw/ars. f/amey fZg/qfiar 160/7 J 5/1044? by may Patented Apr. 12, 1927.

' UNITED STATES PATENT OFFICE.-

rLErcnEa, or NEW YORK, n. Y., AND LEon .1. srvmn, or IBLOOHIIELD, NEW JEEsEY, ASSJIGNOBS 'ro WESTERN ELEc'rnIc couramr, mconroEa'rEn, OF" NEW YORK, 11. 1., a coarona'rron or NEW YORK.

BINAU RAL TELEPHONE SYSTEM.

Application filed June 15, 1925. Serial No. 37,050.

This invention relates to a binaural transmission system designed to transmit sound with substantially the same naturalness as obtains in transmission through the air. The transmitters are mounted in a dummy or artificial head which produces a sound shadow similar to that of a human head and secures a sound pick-up simulatlng that of a listener similarly positioned. The transmitting paths may be metallic, carrier or radio channels, and-may. include recording links such as phonograph records.

An object of this invention is to provide a transmision system. which gives to the listener impressions of location of the source of the sound with relation to the pick-up point with relatively the same naturalness as obtains by the ordinary transmission of sound through the air direct. This requires accurate preservation of the pressure variations on the ear drums of the listener both in phase and in amplitude, particularly the latter. This result is obtained by employing with the dummy orartificial head a binaural telephone pick-up,. and amplifying, transmitting, and receiving apparatus, each portion of which has a frequency characteristic which is practically flat. over a range between about. 30, and'12,000 cycles. This system may be employed for making bin-.

aural phonograph -records by replacing the head receiver with suitable recording members.

In high quality telephone systems binaurally associated and having the transmitters lo,-

I cated in a dummy head designed to have the same efieet upon sound waves reaching it as the head of the listener located in the same position.

In accordance with a s ecific' application of this invention pick-up e ectrostatic or condenser-transmitters, mounted in a, dummy .head, audion distortionless amplifiers, and electrostatic or condenser-receivers are employed in a binaural system, the overall airto-ear frequency characteristic of each channel ofthe combination being practically uniform throughout the entire important audio frequency range. Airtight connection be tween the external ear and the condenserreceivers is nnportant and may besecured by placing ring pads or gaskets of sponge rubber or other suitable material between the ears and the receivers. Any leakage between the receivers and ears causes undesirable resonances at definite frequencies in the air chambers formed by the receivers and the external ears. A high degree ofuniformity in frequency response is essential and is obtained by this system.

poor. The applicants system largely overcomes the poor quality characteristics menneral, this invention comprises two tioned above and bothsustained and unsustained sounds taking place anywhere in a large room are transmitted and reproduced with a'naturalness almost equalingth'at obtained by direct hearing. The usual boominess andexaggerated reverberations accompanying distant pick-up are largely elimi- 1 ing the source of sound b t in none of these systems, to the best of app 'cants knowledge,

is the naturalness of the sounds preserved with the utmost accuracy. For such systems extremely sensitive microphones have been employed with reasonable satisfaction from the standpoint of articulation or volume but not from the standpoint of avoiding distortion and ofpreserving the naturalness of the direction and quality of the sound over the entire audio frequency range. While a disreproduction, are reproduced with' transmitters. The latter is accomplished by -carrier channels.

certain amount of distortion which in the present system isavoided by employing condenser type transmitters and receivers. This system is characterized from the prior art by the employment in a binaural s stem of distortionless. receivers, distortio ess ainslifiers, distortionless transmitters, and a istortionless arrangement of the pick-up the employment of a dummy head in which the transmitters are mounted in opposite sides facing in opposite directions.

Referring to the drawings, Fig. 1 is a diagrammatic representation of the system; Fig. 2'shows the circuit for one-half of the s stem; Fig. 3 shows a cross-section of a ummy head;'Fi 4 is an external view of a dummy head; ig. 5 shows an edge view in partlal crom-section of the condensertransmitter and condenser-receiver; and Fig. 6 shows a front side view of Fig. 5.

Similar reference characters designate similar parts in the different views.

Referring garticularl to Fig. 1, which is a schematic rawing o the system, 10' and 11 designate the 'r' ht and left circuits, 12 and 13 the ri ht an left condenser-receivers, 14 and 15 t e distortionless right .and left amplifiers, 1'6 and 17 the right and left condenser-transmitters, and 18 the dummy or artificial head in which the transmitters are mounted. While the circuits 10 and 11 are shown as simply pairs of wires it will be understood that .in practice the may be any suitable transmission paths suc as radio or An example of a radio system to whichone channel 10, or 11 may be applied is given in Shreeve Patent 1,878,982 Ma 24, 1921. The second'radio .channel wou d be a duplicate of the first.

If only one-way transmission is desired, the corresponding side of the Shreeve system can be omitted. .This system is applicable for making binaural honograph records by substituting a pair '0? suitable recorders for the receivers." The recorders may consist of electrically operated cutting styluses assoclated with mechanically cut records or of an other suitable type.

i 2 shows the distortionless audion amp er of the resistance and choke coil coupling l type which provides amplification of very igh quality. Other types of amplifiers rovlding distortionless amplification may used. As the arrangement of the amplifier is obvious from the drawing and particularly since amplifiers of this character are well known in the art a detailed description is omitted. For a detailed description of a similar amplifier, reference may be had to an articleentitled The nature of ee'ch and its interpretation by Fletcher, rnl Franklin Institute, June, 1922! Fig. 3 shows a cross-section of the dummy head and the preferred location of the condenser-transmitters 16 and 17. The head is made of and stuffed with material which" practically free from any vibrational effects other than those transmitted to it through the air.

Figs. 5 and 6 show the condenser-transmitters and condenser-receivers which are similar in design to those shown in the E. G. Wente Patent 1,333,744 of, March 16, 1920. Attached to the front of the receivers is means for making airtight contact tween the receiver and the ear, which con ists of a ring 21 of soft rubber or other similar material.

The results obtained with the above described systcm are almost incredibly surprising and of uncanny realism.

the observer is at a distance from all sounds or' is in a sound insulated booth with the pick-u devices 16 and 17 in a room, forexamp e,- in which persons are moving about,

the observers impulse is to press the re-v ceivers more tightly a ainst his ears to shut out what appears emp atically to him to be side noise gettin to his ears directly from the room by lea age around thereceivers. In reality, however, the interior of the booth is practically silent and all that the observer hears comes throu h the receivers. In other words, it is difiic t for the observer to convince himself that sounds near the transmitters 16 and 17 are not actually and phys-" ically in the same relative position with respect to his own cars. lieved to be the nearest approach to a completely natural reproduction of sounds ofany heretofore realized and gives the listener a sense of acoustic perspective comparable to the optical perspective obtained from stereoscopic views.

This system may be applied to radio broadcasting by using radio channels and it may also be used in the recording and the reproducing of phonograph records. In each of these applications, as well as in others, the sense of location of the sound due '.to the binaural arrangement is" im' ressed.

upon the listener, and with substantia ly distortionless transmission .throu bout the audio frequency range as is o tainedlto an unusual degree by this system, naturalness of reproduction is obtained to.an unusual When the sys-'- tem is properly arranged and adjusted, and

This result is becations within the scope of the appended claims may be made without departing from the spirit of the invention.

What is claimed is:

1. A binaural transmission system for transmitting sound substantially distortionlessly and for enabling the listener to perceive the sounds both in relation to their source and with naturalness as though transmitted through the air, comprising a pair.

of pick-up transmitters mounted in a dummy head, means for amplifying sound, a. pair of telephone receivers, one for each ea-rof said listener, and a separate circuit connecting each of said pick-up transmitters through a respective amplifying means with a corresponding receiver, each of said elements aifording substantially distort-ionless operation.

'2. A binaural telephone system' for enabling the listener to receive transmitted sounds with a-sensation of substantially the same relation to the source of sound as would exist were the sounds transmitted through the air, comprisinga pa1r of distortionless condenser transmitters mounted with relation to each other the same as the cars of a listener, a air of distortionless condenser telephone receivers,- one for each ear of said listener, a air of distortionless current amplifiers an apair of separate circuits each includin one of said current amplifiers and connecting each of said transmitters with a corresponding one of said receivers. a

3. A binaural telephone system comprising a pair of pick-up condenser-transmitters, a corresponding pair of condenser-receivers and separate amplifying circuit connectingeach of said transmitters with the corresponding receiver, and means for positioning said pick-up transmitters with respect to the reception of sound in relation to each other and 11nder conditi0ns simulating those to which the organs of hearing are normally subjected, said means comprising a body about the size and configuration of the human head, and having reflecting and diffracting qualities substantially similar to those of the human head.

4. A binaural telephone system comprising a pair of pick up transmitters, a dummy head for mounting said transmitters, a corresponding pair of telephone receivers, a

. separate amplifying circuit connecting each of said transmitters with the corresponding receiver, and means for effecting equal amplification in each of said circuit-s, each of said elements transmitting substantially without distortion.

-5. In abinaural telephone system comrisin a air of condenser-transmitters mounted on opposite'sides of a sound shadow casting member, said member consisting of a body about the size and shape of a human head and made of sound reflecting and fracting material substantially the same as that of the human head, a pair of condenserreceivers, one for each car, a separate cir- 1 end connecting each of said transmitters with a corresponding one of said receivers and an amplifier in each of said circuits, each of the above enumerated elements transmitting substantially without distortion throughout the audio frequency range.

6. In a biiiaural telephone system, the

combination of two condenser transmitters,

a sound shadowcasting member mounting said transmitters, two amplifiers, two condenser receivers, and two circuits connecting the two respective sets of apparatus into 9.

binaural system, each of the above enumerated transmission elements giving substantially distortionless transmission throughout a frequency range of from the order of thirty to the order of twelve thousand cycles per second. i

7. In a binaural telephonev system comprising a pair of telephone transmitters, a sound shadow casting member for mounting said transmitters to simulate the eIect of the human head on sound reaching the said transmitters, said means consisting of a dummy head mounting the transmitters on the opposite sides and composed of material reflecting and ditl'racting the propagation of sound substantially the same as the human head, a pair of receivers one for each ear,

9. A binaural system comprising a pair 4 of pick-up transmitters, a dummy head for mounting said transmit-ters, acorresponding pair of receivers, a separate transmission channel connecting each of said transmitters with a corresponding receiver, and means for eiiecti'ng equal amplification in each of said channels, each of said elements operating substantially without distortion.

10. In a binaural system comprising apair of pick-up dlstortionless condenser transmitters, a-d-ummy head for mounting said transmitters a receiving station having a pair of duplicate receiving means, a separate transmission channel connecting each of saidtransmitters with the corresponding receiving means,fa nd means forefiecting substanear of said listener, and a separate channel tially equal amplification in each of said channels. 11. A binaural system, comprlsing a pair of pick-up distortionless transmitters mounted on opposite sides of a sound shadow casting member, said member consisting of abody about the size and shape of a human head and made of sound reflecting and diffracting material Substantially the same as that of the human head, a receiving station having a pair of duplicate receiving means, separate amplifying'circuits connecting each 1 of said transmitters'with the corresponding dummy head, means for amplifying sound,

a pair of telephone receivers, one for each connecting each of said pick-up transmitters through a respective amplifying means with a corresponding receiver, each of said channels aflording substantially distortionless operation,

13. A binaural transmission system for transmitting sound substantially distortionlessly and for enabling the listener to perceive the sounds both in relation .to their source and with naturalness as though transmitted througlr'the'air,comprising a pair of pick-up transmitters; mounted in a dummy head, means for amph-fyingsound, a pair of telephone receivers, one for? each ear of said listener, and a-separate carrier or radio channel connecting each of said pick-up transmitters through a respective amplifying means with it comes ending receiver,

each of said, channels afl'o g su consisting of a body substantially t e size and shape of ahuman head iandia transmitters mounted on the-head their relation to each other substantially the same as the human ears. 1

- 15. In a binaural system, a dumm head; consisting of a body substan lly t e size,

and shape, of a human head-5 d a pair of distortionless condenser-transmitters mounted on the head with relationvto -each other substantially the same as the human ears.

16. In a binaural system, a dumm head consisting of a body substantial-l t e size and shape of a human head an i-.. made of sound reflecting and difi'ra'cting 'material substantially the same as thatof the human head and a pair of transmitters mounted upon the head with relation toeach other substantially the same as the human ears.

In witness, whereof, we hereunto subscribe our names this 13th day of June A. D., 1925.

HARVEY FLETCHER. LEON J. SIVIAN.

stantiallji' nhdlstQrtiOIllGSs operation. 3

14. In a binaural system, a dumm head; 

